Expellable cartridge case

ABSTRACT

Novel cartridge, suitable for use with high velocity anti-tank projectiles, possesses an open tube casing adapted to be expelled from the weapon along with the projectile and separated therefrom on muzzle exit, thereby eliminating dangerous residues in the weapon without significantly affecting projectile ballistics. The cartridge has an open ended casing attached by means of an adapter to the rear of a projectile provided with a tracer composition and an obturating band. The casing is closed at its breech end by a ventable cap and the adapter at the other end is open so that the propellant gases can pressurize the breech area and entire gun area behind the obturator band and expel the projectile. The adapter also permits the propellant gases to ignite the tracer composition so as to burn and sever the attachment to the projectile. The attachment remains intact while the cartridge is in the gun barrel but is severed after it leaves the muzzle, whereby the projectile is separated from the adapter and spent casing debris in the area near the front of the weapon and no residue, fragments, etc. are left behind in the weapon.

United States Patent Blajda Aug. 7, 1973 i 1 EXPELLABLE CA TR CASE Primary Examiner-Robert F. Stahl [75] Inventor: Raymond S. Blajda, Parsippany, NJ. Harry saragov'tz Edward Kelly e a. [73] Assignee: The United States of America as [57] ABSTRACT "Presented P) the Santa" the Novel cartridge, suitable for use with high velocity anti- Army, Washington tank projectiles, possesses an open tube casing adapted to be expelled from the weapon along with the projecl Flledi J 4, 1972 tile and separated therefrom on muzzle exit, thereby [2l] Appl. No.: 215,364 eliminating dangerous residues in the weapon without significantly affecting pro ectile ballistics. The cartridge has an open ended casing attached by means of U.S. an adapter to the rear of a projectile provided a 102/DiG- 7 tracer composition and an obturating band. The casing {S In. C. t t t 1 is closcd at its breech end a ventablg cap and the 0' Search 43, p, adapter at the other end is open so that the propellant 102/931 52 gases can pressurize the breech area and entire gun area behind the obturator band and expel the projec- [56] Rekrences cued tile .tTl: apaptcr also pe zrnits the proiellant ggses to 1gn1 e e racer compos1 101'] so as o urn an sever UNITED STATES PATENTS the attachment to the projectile. The attachment re- 3'609'904 10/197 scfmlon 02/43 P mains intact while the cartrid e is in the un barrel but 2 389 846 ll/l945 F 102/93 8 8 1 7/1966 a g 02/93 is severed after it leaves the muzzle, whereby the projectile is separated from the adapter and spent casing 16581108 4/1972 Larson 102/43 P 3,527.13? M970 Scanlon u '02, P debris 1n the area near the front of the weapon and no 3,620J67 11 1971 Romeret al. 102 93 residue fragments, are left behind the p 6 Claims, 1 Drawing Figure EXPELLABLF. CARTRIDGE CASE The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION The present invention relates to a novel cartridge suitable for use with large caliber ammunition, wherein the casing is of an open tube design and is expelled from the weapon together with the projectile by means of the gas pressure generated from the propellant act ing against an obturating band located on the projectile.

Conventional ordnance ammunition consists of a metal casing containing a propellant charge and a projectile forming a single structure or cartridge, which is placed into the breech of a cannon and fired, whereby the projectile is shot from the cannon at a high velocity. Usually the cannon is provided with an ejector mechanism for removing the metallic casing after the cartridge has been fired. Conventional cartridges of this type are unsuitable for use in military tank cannons since ejection of the metallic casings into the tank would be intolerable due to space limitations within the tank and introduction of toxic gases attending the opening of the breech.

Much effort and expense have been applied to overcome this problem. Thus, the metallic cartridge case has been replaced by a non-metallic casing containing highly inflammable nitrocellulose, which is consumed on firing of the propellant charge. It has also been pro posed to provide a casing of an organic plastic material, c.g. a glass fiber reinforced polyester resin, having a plurality of structurally weak areas, whereby the pressure of the propellant gases causes the casing to break into small fragments which burn and disintegrate and are blown out of the weapon. The use of such consumable or frangible cartridge casings eliminates the need for an ejection mechanism and opening of the breech of the cannon. However, such cartridge cases are relatively fragile and the nitrocellulose is easily degraded by water and oils with the result that the cartridge, after firing, occasionally leaves fragments and smoldering residue, which constitute a serious hazard as it can ignite subsequent rounds.

It is therefore a principal object of this invention to provide a novel cartridge, wherein a projectile carrying an obturator is attached to an open tube casing containing a propellant charge, which will be completely expelled from the gun barrel in conjunction with the projectile when the cartridge is fired, and separated therefrom on muzzle exit.

A further object of the invention is to provide a cartridge, wherein a high velocity, fin-stabilized projectile mounting an obturator is attached to an open tube casing containing a suitable propellant, and wherein the casing is attached at its forward open end to the rear of the projectile by means of a device adapted to be disconnected therefrom by a pyrotechnic charge situated in the projectile and ignited by the propellant burn.

Other objects and advantages of the present invention will appear or be obvious from the following detailed description in conjunction with the accompanying drawing.

SUMMARY OF THE INVENTION The aforesaid difficulties of the prior art are obviated and the objects of the invention are achieved by the novel cartridge which possesses an open tube cartridge casing adapted to be expelled from the gun barrel along with the projectile and to be separated therefrom after expulsion so as not materially to affect the ballistic properties of the projectile. Thus. after firing of the cartridge, no dangerous smoldering or other residues are left in the gun barrel and the need for means for removing a used casing from the fun breech is eliminated.

In general, the novel cartridge comprises a. a projectile;

b. a propellant charge for propelling the projectile;

c. an open ended non-combustible cylindrical car tridge casing containing the propellant charge;

d. a ventable closure for the breech end of said casing, i.e. one which burns away or vents to permit the propellant gases to pressurize the breech area;

e. an obturator attached to the projectile to seal the gases so as to propel the projectile; and

f. means for attaching the forward end of the casing to the rear of the projectile, said means permitting passage of propellant gases from the casing to the obturator and being adapted to separate from the projectile by the action of the propellant gases after leaving the gun barrel, whereby said means and easing follow the projectile in the gun barrel and separate from the projectile when it leaves the weapon without significantly affecting the ballistic properties of the projectile.

The invention is particularly directed to a cartridge of the foregoing design, wherein the projectile is a fin stabilized, high velocity (eg 5000 ft./sec. or more) missile and the open tube casing is relatively long due to its content of a large amount of propellant needed to provide the high pressures {c.g. 60,000 psi or higher) required for propelling the high velocity projectile. The complete removal of such long, noncombustible cartridge casings associated with high velocity, finstabilized projectiles presents an especially difficult problem which is satisfactorily overcome by the present invention.

In a particular embodiment the projectile is provided with a pyrotechnic composition, which is adapted to be ignited by the propellant burn and thereby sever the attaching means from the projectile.

DETAILED DESCRIPTION OF THE INVENTION The drawing illustrates a longitudinal sectional view of an expellable cartridge of this invention.

Referring to the drawing, there is shown I52 mm. cartridge comprising an open ended cylindrical casing I0 approximately 63 cm. long, fabricated of high density polyethylene or other suitable material and not combustible under the firing conditions. Casing I0 contains a propellant charge ll for generating the desired pressure. The breech end of casing 10 is closed by cap 12 having a cup 13 containing an initiator (not shown) for a booster charge of black powder etc. contained in a plastic bag (not shown) for igniting the main propellant charge. The base cap I2 is attached to casing I0 with an epoxy resin or other suitable adhesive and is composed of conventional combustible material which is consumed under the firing conditions and thus allows the propellant gases to pressurize the breech area of the gun. The forward end of casing is attached to a rigid, wheel-like adapter 14 of high density polypropylene having a hub 15 joined by four equally spaced, radial spoke members 16 to a flat rim 17, which is peripherally joined to casing 10, e.g. by adhesive bonding, riv ets, etc. Hub 15 is provided with screw threads 18 for attachment to threaded cavity l9 in the rear of tungsten steel projectile 20, and a hole 21 for passage of propellant flash to a tracer charge (not shown) contained in cavity 19.

Projectile has four equally spaced, full caliber fins 22, which fit into sealed slots in the forward end of casing 10. (Subcaliber fins can also be used, obviating the need for slots in the casing). Four full caliber steel sabot blocks 23, as quadrantal sections, are removably mounted on the low caliber cylindrical body of projectile 20 by means of buttress threads or the like, which prevent sliding movement but permit release of said blocks by centrifugal force generated by the spinning projectile. Four quadrantal sabot blocks 24 of polypropylene are placed around steel sabot blocks 23 and are held in place by a tight fitting annular obturating band of polypropylene. The obturating band 25 is engraved with grooves, which cause the obturator band to break into pieces by spin and thrust forces on exiting from the gun muzzle.

In operation, ignition of propellant 11 by initiator l3 and the black powder booster charge causes generation of gas pressure and combustion of cap l2, thereby venting gases to pressurize the breech area of the gun. The gases penetrate between the casing 10 and the gun wall, and also pass through the open forward end of casing 10 and open adapter 14, thereby exerting pres sure against the projectile-sabot-obturator assembly. This pressure causes obturating band 25 to slide forward along the inclined surface of sabot blocks 24 and thus expand and wedge against the gun barrel wall, thereby sealing the gases behind the projectile-sabotobturator assembly and propelling the projectile and attached adapter and easing through the gun barrel and engraving the rifling of the bun barrel to provide projectile spin. Obturating band 25 is provided with a tongue extension 27, which overlaps casing 10 for a sufficient distance so as to maintain such overlapping and gas seal function even when the front end of obtu rating band 25 reaches the rear edge 26 of steel sabot 23, which stops its forward travel. Further, the hot combustion gases pass through hole 2] in hub 15 of adapter wheel 14 to cavity 19, thereby igniting the tracer charge in cavity 19 for marking the path of the projectile 20. The heat from the burning tracer charge melts and destroys screw threads l8 in such a manner that adapter [4 and casing 10 remain attached to the projectile in the gun barrel but are separated from the projectile on exiting from the weapon. Due to the enormous internal gas pressures, the casing N] on exit ruptures explosively into shreds and fragments, which together with the adapter 14 separate from the projectile essentially in the cone of tire region in front of the weapon along with debris from the obturating band 25 and sabot elements 23 and 24, which are separated from the spinning projectile by centrifugal force, as noted above.

Inspection of the breech after firing of the novel cartridge showed no evidence of residue or fragments so that the weapon could be safely and repeatedly reloaded and fired with automatic reloading mechanism (not shown) using the aforesaid ammunition without the need to open the breech for any reason.

Due to the open tube design of the casing used in the novel expellable cartridge of the present invention, an obturating band is required to seal and confine the propellant gases behind the projectile. The obturating band can be made of materials conventionally used for such purpose, preferably a tough flexible organic plas tic material, e.g. polyethylene polypropylene and nylon, although a soft malleable metal e.g. copper, gilding metal etc. can be employed. Further, the obturator can be installed in any suitable manner, e.g. as a fixed annu lar ring on a cylindrical projectile slug or shell of sub stantially full caliber size. Advantageously, the obtura tor band can be installed in a non-fixed manner directly on the projectile shell, etc. or on sabot elements attached to the projectile, the sabot-obturator-projectile assembly design being such that the propellant gases will move the obturating band forward up an inclined plane, as illustrated in the drawing, sufficiently to expand and prevent the escape of gases past the projectile and also to engage the rifling of the weapon and thus impart sufficient spin to the projectile to remove the obturator and sabot elements by centrifugal force.

With high velocity fin-stabilized projectiles of the type illustrated above, pressures of the order of 60,000 80,000 psi are usually developed in the gun. Such projectiles depend essentially on fins for flight stability, but are usually imparted a low spin (e.g. 30 rps) sufficient to prevent yaw, etc. as well as to remove sabot el ements and obturator band by centrifugal force. In con trast, spin-stabilized projectiles require a much higher order of spin (e.g. 1000 rps and higher) and relatively low pressures (e.g. 30,000 psi) to achieve gyroscopic flight stability.

Particularly for use with such high velocity projectiles the cartridge casing is desirably made of a flexible organic plastic, including a thermoplastic or thermosetting resin, preferably having an elongation of at least about 400 percent, and especially about 500 l000 percent, such as for example high density polyethylene and polypropylene. Highly malleable metals possessing similar elongation, e.g. tin and aluminum, are also suitable. However, organic plastics generally provide advantages in cost and ease of fabrication of the casing and are hence preferred. Casings fabricated of relatively rigid or brittle plastic, such as polyacetal resin, tend to fracture under such high gun pressures and explosive shock and leave fragments behind, whereas a flexible casing of polyethylene travels through the gun barrel essentially intact.

The obturating band and sabots can be made of materials conventionally used for the purpose, e.g. high density polypropylene and polyethylene, similar to that employed in the casing.

The base cap of the cartridge casing can be of a combustible type, e.g. a conventional molded nitrocellulose-Kraft fiber-resin mixture; or it may be an organic plastic or metal plate containing holes through which the propellant gases can be vented so that the pressure thereof is not applied against the base cap but rather is applied to the breech area to expel the cartridge. To contain and protect the propellant charge in the casing prior to firing, the holes are covered with a suitable material, e.g. thin plastic sheet, which will fail before the closure cap on firing of the propellant.

The design of the adapter for attaching the casing to the projectile can be varied so long as it permits passage of the propellant gases out of the casing to press against the obturating band. Thus, the adapter can be a circular type frame, eg a wheel, peripherally attached to the casing and connected by strong radial spokes or equivalent structure to a hub, which is fastened to the rear of the projectile by screw threads, bolt, or other suitable locking means capable of being melted, burned or otherwise destroyed by the hot propellant gases, or by a tracer or similar composition contained in the projectile ignited by the hot propellant gases. In a preferred embodiment the adapter hub is attached, cg. by screw threads to a cavity, which is lo cated in the rear end of the projectile and contains a tracer composition. The hub has a hole through which the propellant gases can pass to initiate the tracer composition, which melts or otherwise destroys the means of attachment, such that the attachment remains intact while the round is in the gun barrel but is severed after the projectile-casing assembly leaves the muzzle, whereby the projectile is separated from the adapter and spent casing debris in the area near the front of the weapon and no residue, fragments, etc., are left in the weapon. The adapter can be made of organic plastic material, e.g. polyolefine such as polyethylene and polypropylene and nylon.

I wish it to be understood that I do not desire to be limited to the exact method and detail of construction described for obvious modification will occur to persons skilled in the art.

What is claimed is:

1. An expellable cartidgc comprising in combination:

a. a fin-stabilized projectile having a low caliber cylindrical shell;

b. sabot elements removably mounted on said projectile shell;

c. an open ended flexible cylindrical casing contain ing a charge for propelling said projectile;

d. a veritable closure for the breech end of said casing permitting the propellant gases to pressurize the breech area;

e. an annular obturating band slidably mounted on said sabot elements and holding the sabot elements together, said obturating band being adapted to be forced forward slidably over the inclined surface of said sabot elements by the propellant gases and thereby to expand and engage the gun rifling and seal the gases behind the projectile; and wherein said obturating band and sabot elements on muzzle exit are removed from the projectile by centrifugal force of projectile spin;

f. means for attaching the front end of said casing to the rear of said projectile, said means permitting passage of propellant gases from the casing to the obturator band and being adapted to separate from the projectile by the action of the propellant gases on muzzle exit, whereby said casing and means follow the projectile in the weapon but are separated from said projectile on muzzle exit without materially affecting the ballistic properties of the projectile.

2. A cartridge according to claim I, wherein the projectile is provided with a pyrotechnic composition adapted to be ignited by the propellant gases and cause separation of said attaching means from said projectile.

3. A cartridge according to claim 2, wherein the easing is fabricated of an organic plastic having an elongation greater than about 400 percent and the ventable closure is a cap which is consumed in the firing of the propellant.

4. A cartridge according to claim 3, wherein said means for attaching the front end of the casing to the rear of the projectile comprises a circular frame, a hub, and spokes connecting the frame to the hub, and wherein:

said frame is peripherally attached to said casing;

said projectile has a cavity containing the pyrotechnic composition; and

said hub is attached to said cavity by a locking means and has a hole permitting propellant gases to pass from said casing to said cavity to ignite the pyrotechnic composition and eliminate said locking means. i

5. A cartridge according to claim 4, wherein said attaching means is fabricated of a polyolefine.

6. A cartridge according to claim 4, wherein said locking means consists of a screw. 

1. An expellable cartridge comprising in combination: a. a fin-stabilized projectile having a low caliber cylindrical shell; b. sabot elements removably mounted on said projectile shell; c. an open ended flexible cylindrical casing containing a charge for propelling said projectile; d. a ventable closure for the breech end of said casing permitting the propellant gases to pressurize the breech area; e. an annular obturating band slidably mounted on said sabot elements and holding the sabot elements together, said obturating band being adapted to be forced forward slidably over the inclined surface of said sabot elements by the propellant gases and thereby to expand and engage the gun rifling and seal the gases behind the projectile; and wherein said obturating band and sabot elements on muzzle exit are removed from the projectile by centrifugal force of projectile spin; f. means for attaching the front end of said casing to the rear of said projectile, said means permitting passage of propellant gases from the casing to the obturator band and being adapted to separate from the projectile by the action of the propellant gases on muzzle exit, whereby said casing and means follow the projectile in the weapon but are separated from said projectile on muzzle exit without materially affecting the ballistic properties of the projectile.
 2. A cartridge according to claim 1, wherein the projectile is provided with a pyrotechnic composition adapted to be ignited by the propellant gases and cause separation of said attaching means from said projectile.
 3. A cartridge according to claim 2, wherein the casing is fabricated of an organic plastic having an elongation greater than about 400 percent and the ventable closure is a cap which is consumed in the firing of the propellant.
 4. A cartridge according to claim 3, wherein said means for attaching the front end of the casing to the rear of the projectile comprises a circular frame, a hub, and spokes connecting the frame to the hub, and wherein: said frame is peripherally attached to said casing; said projectile has a cavity containing the pyrotechnic composition; and said hub is attached to said cavity by a locking means and has a hole permitting propellant gases to pass from said casing to said cavity to ignite the pyrotechnic composition and eliminate said locking means.
 5. A cartridge according to claim 4, wherein said attaching means is fabricated of a polyolefine.
 6. A cartridge according to claim 4, wherein said locking means consists of a screw. 